This invention relates generally to media handling mechanisms, and more particularly to techniques for maintaining the top level of a stack of media sheets in a printing device.
A printing device, for example a printer, normally includes an input tray for accommodating a stack of media sheets. During printing operations, a pick mechanism in the printer continuously picks and feeds an individual media sheet atop the media stack to a print zone for imprinting images on it. As the media sheets are consumed, the media stack height decreases. Normally, such a decrease in the media stack height would lead to a decrease in a top level of the media stack and consequently an increase in a displacement between the pick mechanism and the top of the media stack. The increase in the displacement may result in a large variation of pick angle or pick force and may inevitably affect pick performance of the printer.
Solutions have been introduced to maintain the top level of the media stack. For example, an electrical motor with a feedback controller can be used to maintain a constant top level of the media stack. However, such a design occupies space and may increase the product cost due to its complexity. In addition, an electrical system may also require a higher electrical power consumption by the product.
Therefore, there is a need for a convenient and effective way to maintain the top level of the media stack in a printing device.